While that's true, I think it's worse for nested comments. The rationale for having nested comments in the first place was the ability to comment-and-forget blocks of code, no matter the contents of the block. I actually think strings should also be parsed too inside nested comments.

Not being able to use unmatched " in comments (and proper escape sequences inside strings) seems only a small price to pay, considering you can't have bare {- and -} in block comments either.

Or perhaps a different kind of comment syntax specifically for commenting out code? Clojure for example has a reader thing #_ that effectively comments out the next form, meaning that its structure has to be a bit like code.